Japanese Laid-Out Patent Publication No. 2005-125949 discloses a mounting structure for an inlet box of a car. As shown in FIG. 16, the user first inserts the cylindrical portion 113 of the inlet box 110 into a hole 103 provided in a recess of an outer panel 101 of the car. A flange 114 provided around the opening of the inlet box 110 is then overlapped on the edge 102 around the hole 103 from the outside. Next, the flange 114 of the inlet box 110 is screwed to the edge 102 of the hole 103 from the outside of the outer panel 101. In this way the inlet box 110 is completely installed onto the outer panel 101. A lid (not shown) capable of closing the recess in the outer panel 101 is connected to the outer panel 101 through a hinge mechanism (not shown).